I don't have a strong interest either, but on a filthy-weather-day a while back that interesting debate came to my attention.
There is also enormous complexity in enforcement of the proposed new rules/tax and, in many respects, that was the most fascinating part of the debate - it covered all of the baser instincts of mankind and how they can overcome the rules, avoid the tax and avoid prosecution. As I mentioned, there are some cunning plans under consideration to deal with this.

As for the trucks in Dover last year, think of Romanian, Bulgarian and other registrations out East; France deal with this via their toll roads and various restrictions of HGVs from their smaller highways.
I don't know much about Germany, but they will be well aware of the situation.
No doubt, similar competition issues exist in those "older" members of the EU.

Incidentally, the professional transport companies will not be paying the banner-headline prices that we mere mortals are expected to pay at the pump. Their own head offices will negotiate the rates for buying in bulk, as I would if I had the purchasing power (some folks in the UK are doing this now for bulk purchase of fuel oil for central heating - a whole village get together and cut a deal with the suppliers - neat eh!)

I have had something of a minor interest, in travelling on our own highways, to study how many/big additional fuel tanks can be fitted onto the prime mover of a HGV - just overtake them slowly and take a look.

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Dave